ONTOGENY AND SYSTEMATICS OF TOERNQUISTIIDAE (TRILOBITA, PROETIDA) FROM THE ORDOVICIAN OF THE ARGENTINE PRECORDILLERA

The following new Toernquistiidae from Whiterockian (Llanvirn to lower Caradoc) strata of the Precordillera, western Argentina, are describe d: Chomntopyge canasi neu species, Lasarchopyge benedettoi new genus a nd species, Lasarchopyge correae new genus and species, Lasarchopyge n ew species A, and Paratoernquistia sanchezae new genus and species. Ph ylogenetic analysis suggests that the Toernquistiidae Hupe, 1953 (incl uding Chomatopyge, Lasarchopyge, Mesotaphraspis, Paratoernquistia, and Toernquistia) is closely related to but distinct from the Dimeropygid ae Hupe, 1953 (including Ischyrotoma, Ischyrophyma and Dimeropyge). it is difficult to find unique synapomorphies that unite toernquistiids and dimeropygids into a monophyletic group that excludes other proetid es (e.g., hystricurids), although details of their ontogenies are simi lar. Several species of Toernquistiidae are known from the Argentine P recordillera (one species previously described), and other species of this family have been described from Australia, Baltica, China, Kazakh stan and Laurentia. Members of the Dimeropygidae are known only from B altica and Laurentia.